Apparatus for electrolytically sharpening the edges of a continuous strip



Aug. 27, 1968 a. w. LOVEKIN 3,399,130

APPARATUS FOR ELECTROLYTIC-ALLY SHARPENING THE EDGES OF A CONTINUOUS STRIP Filed April 26, 1965 2 Sheets-Sheet 1 INVEMm 54/"? M/M/mm Lo uakm A-rw-onusv 9 Aug. 27, 1968 a. w. LOVEKIN 3,399,130

APPARATUS FOR ELECTROLYTICALLY SHARPENING THE EDGES OF A CONTINUOUS STRIP Filed April 26, 1965 2 Sheets-Sheet 2 Havana-roe ATTORNEY;

United States Patent 3,399,130 APPARATUS FOR ELECTROLYTICALLY SHARPENING THE EDGES OF A CON- TINUOUS STRIP Barry William Lovekin, Langley, England, assignor to Wilkinson Sword Limited, London, England, a British company Filed Apr. 26, 1965, Ser. No. 450,718 Claims priority, application Great Britain, May 14, 1964, 20,032/ 64 2 Claims. (Cl. 204-206) ABSTRACT OF THE DISCLOSURE The invention provides a method of forming the cutting edges on razor blades by passing the razor blade material through an electrolyte whilst the material is maintained at an anodic potential. The major portion of the central area of the material is masked so that current flows from each unmasked edge into the electrolyte. For mass production, current densities of the order of 200 amps per square inch at the edge of the material are employed together with high flow rates of electrolyte, such as 30 gallons per minute under a high-pressure, such as 100 lbs. per square inch.

This invention relates to the production of cutting edges and Whilst relating particularly to the production of the cutting edges of razor blades is not limited thereto.

More particularly, the invention employs electrolytic processing in the production of cutting edges. The electrolytic processes may be used for the finishing, only, of cutting edges after initial formation by other methods, such as abrasive methods, and such processing will be referred to hereafter as electrofinishing. On the other hand, the processing may be used for production of a cutting edge, Without prior mechanical shaping, in which case such processing will be referred to hereafter as electroforming.

The novel features of the present invention will be better understood from a consideration of the following description of one method of, and apparatus for, the electroforming or electrofinishing of cutting edges, the description being by way of example and with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic representation of the complete apparatus;

FIGURE 2 is a perspective view, partly broken away, of the cell in which the eletcrolyte treatment is effected;

FIGURE 3 is a sectional view through a mid-portion of the cell of FIGURE 2;

FIGURE 4 is a sectional side elevation of one end of of the cell; and

FIGURE 5 is a similar view to FIGURE 3 of a modified construction of cell.

The method and apparatus will be described with reference to the formation of cutting edges on steel strip to provide double-edge or single-edge razor blades.

Conveniently, the strip to be electrolytically processed is in the state in which it normally is prior to formation of the cutting edge by conventional abrasive means, that is to say, it may consist of blade blanks of appropriate configuration which are united end-to-end in the form of a strip and which, after formation of the final cutting edge, merely require separation from one another to provide finished blades ready for shaving. If the electrolytic processing is to be limited to electrofinishing, the strip will have been subjected to partial edge formation by mechanical or other methods.

The electrolytic treatment is effected in a cell having the form shown in the accompanying drawings. As indicated diagrammatically in FIGURE 1 the strip 9 is drawn into the cell 10 from a supply spool 11 and after its withdrawal from the cell is submitted to a rinsing treatment in a rinsing bath 12 followed by a drying treatment in a dry chamber 13. It is then drawn by a strip driving member 14 powered by a motor 15 onto a collecting spool 16 for further processing or the finished blades are separated from one another for wrapping and/ or packing into dispensers.

The cell and its operating parameters are chosen so that anodic diminution is completed during the continuous passage of strip through the cell 10. I

The tubular metal wall of the cell 10 constitutes the cathode and the anode is provided by two contact strips 20 and 21 between which the blade strip 9 passes on its passage through the cell 10. The contact strips 20 and 21 are respectively mounted in electrically insulating inserts 22 and 23 secured to the cell Wall and the contact strips 20 and 21 are held in engagement with the blade strip 9 by virtue of springs 24 which urge the lower contact strip 20 upwardly. The lower contact strip 20' extends from both ends of the cell 10 and an electrical power supply is connected to this external portion at terminal 25 and to the wall of the cell 10 at terminal 26. The end plates 10a, 10b, of the cell 10 through which the lower contact strip 20 project are insulated from the tubular wall of the cell 10 by end caps of insulating material. The insulating inserts 22 and 23 in which the contact strips 20 and 21 respectively are mounted are shaped to provide flow channels for electrolyte adjacent each edge of the razor blade strip 9. The contact strips 20, 21 serve to mask the major portion of the surface of the razor blade strip 9 leaving, for example, only about one eighth of one inch (three millimetres) of each edge exposed, in order to allow the electrolytic action to occur only at the edge of the razor blade strip 9, thereby minimising the area on which diminution can be effected. The other surfaces of the contact strips 20 and 21 are largely masked by the insulating inserts 22 and 23 in which each is mounted.

The electrolyte is forced through the flow channels in the cell 10 under pressure by a pump 9 (FIG. 1) which pumps the electrolyte from a reservoir 17 through cell inlet 10d, the electrolyte leaving at cell outlet 10c and being returned to the reservoir 17. The temperature and composition of the electrolyte, the rate at which it is pumped and its degassing can be controlled at the reservoir.

Typical electrolyte compositions are a mixture of phosphoric acid and chromic acid or phosphoric acid and glycerine. The composition of the electrolyte is chosen carefully from these or other mixtures to obtain the optimum results required and careful control of the composition assists in maintaining stable production conditions. Additives can be advantageously used to control the conductivity of the electrolyte, to facilitate wetting and the removal of gas bubbles, to inhibit decomposition of the electrolyte, to produce a more corrosion resistant finish and to increase the sharpness and durability of the edge.

The cell illustrated in FIGURES 2 and 3 is suitable for electrofinishing. If electroforming is required other or modified methods must be employed. For example, electroforming could be effected by impingement of jets of electrolyte from one or both sides of the strip. Conveniently, however, the same process and cell described for electrofinishing can be used for complete electroforming of the cutting edges or razor blade strips which have not been subjected to initial edge formation, but in this condition the electrode configuration is critical and there should be a relatively small gap between the anode and cathode. This can be achieved, as shown in FIGURE 5, by providing internally projecting cathodes on each side of the inner wall of the cell tube, the surface of these cathodes 10 terminating a short distance from the edge of the razor blade strip 9, for example, of the order of twenty thousandths of an inch (one half of a millimetre).

It will be understood that for a given cell length and initial edge condition, the rate of anodic diminution is proportional to the magnitude of current flow. For a given operating current there is a minimum electrolyte flow rate below which pitting and overheating of the surface may occur. The operating current and therefore processing speed is limited only by the electrolyte flow rate and the current carrying capacity of the contact strips. High current densities of, for example, 200 amps per square inch, may be used in order to obtain a fast processing rate. This involves flow rates of electrolyte of up to gallons per minute at pressures up to 100 pounds per square inch.

The use of high pressure assists to eliminating from the electrolyte bubbles of gas which are liberated during processing. Mechanical means may also be employed to reduce gassing, for example, vibration of the cell particularly by an ultrasonic vibrator. Chemical additives for this purpse have already been mentioned. Depending on the elfect desired in the finished blade A.C. or A.C. superimposed on DC. may be chosen instead of DO for either electrofinishing or electroforming. Advantageous effects for certain materials and electrolytes may be obtained by using power supplies stabilised to produce a constant voltage drop between the anode and the solution, or to maintain the cell current constant, or some other selected combination of current and voltage.

One particular advantage of electrolytic processing is that a desired cross-sectional shape of the cutting edge may be obtained by variation of the electrode relationship, the solution composition, the electrical supply characteristics (including voltage cycling), the temperature and other operating conditions, thus permitting the production of cutting edges of cross-sectional shapes which are difficult or impossible to attain by abrasive methods, for example, a gradual convex curvature towards the tip.

Another advantage is that this technique does not cause mechanical damage to the structure and avoids undesirable effects resulting from the high temperature associated with abrasive metal removal.

Other advantages of electrolytic processing over abrasive methods are that it leaves the edges of the blades free from the included grit and waxy impurities common to abrasives, and instrumental control of the process can be effected more directly using the current/voltage characteristics of the cell.

Apart from the formation or finishing of cutting edges, the system described can also be used for cleaning of strip which can result in increased corrosion resistance due to the removal of foreign matter.

Electroforming is also particularly useful where it is difiicult to employ conventional abrasive methods for the production of a cutting edge. Examples of this are where the razor blade strip is very narrow or where the cutting edge is provided only by a small metal insert in a supporting body of a material such as plastic or ceramic.

Clearly, the invention may be applied to the production of cutting edges other than those of razor blades.

As mentioned hereinbefore it is convenient to process blade blanks united end-to-end in the form of a strip. It will be appreciated that other ways of continuously processing blade blanks may readily be employed. Thus, the blade blanks may be separated, instead of being joined end-to-end, and converged through the electrolytic cell by attachment to a conveyor belt whilst electrical contact to the blanks is effected by contact strips as previously described.

I claim:

1. Apparatus for manufacturing razor blades from a strip of razor blade material, comprising a tubular elongated electrolytic cell having a metal wall, said cell having an inlet for said strip at one end and an outlet for said strip at the other end, means for drawing said razor blade strip through said cell from said inlet to said outlet between said first and second electrical contact strips, a pump for continually circulating electrolyte under pressure through said cell in a direction opposite to the direction of movement of said strip, first and second insulating members each mounted on the inner surface of the wall of said cell, a first electrical contact strip supported by said first insulating member within said cell, a second electrical contact strip supported by said second insulating member in facing relationship to said first electrical contact strip, and means for electrically connecting a cathodic potential to the metal wall of said cell and an anodic potential to said first and second electrical contact strips, said contact strips masking the central portion of said razor blade strip located between regions adjacent the edges whereby electrolytic dissolution of the unmasked edges forms a cutting edge therealong.

2. Apparatus according to claim 1, wherein said cell wall projects inwardly to provide a cathode adjacent each edge of the strip in close proximity thereto.

References Cited UNITED STATES PATENTS 3,281,287 10/1966 Edstrom et al. 148-124 2,930,739 3/1960 Burnham 204-28 2,974,097 3/ 1961 Ramirez et al. 204-206 FOREIGN PATENTS 14,580 1897 Great Britain.

ROBERT K. MIHALEK, Primary Examiner. 

